Rubber compounds are typically vulcanized using various amine containing accelerators such as sulfenamides, thiocarbamyl sulfenamides, thiuram mono- or disulfides, dithiocarbamates, etc. These accelerators are generally based on secondary di-n-alkylamines and aliphatic cyclic amines which are known to generate high amounts of the corresponding N-nitrosodialkylamines. Recent worldwide environmental concerns have stimulated efforts toward finding suitable alternative accelerator systems for abating or eliminating the formation of N-nitrosodialkylamines during the vulcanization of rubber products.
Although a wide variety of thiuram disulfides, based on secondary amines, have been found to be accelerators, none have been shown to provide for excellent curing characteristics without the formation of N-nitrosamines.
The use of alkaline earth oxides and hydroxides in conjunction with secondary amine containing accelerators and conventional vulcanizing agents to reduce nitrosamine levels by at least 20 percent and up to as much as 95 percent has been disclosed by U.S. Pat. No. 5,070,130 to Chasar.